This proposal requests funds to purchase a Hewlett Packard Gas Chromatograph/Mass Spectrometer Model 5988A to be used by a large group of clinical investigators at the Tufts University School of Medicine. The users group includes a wide range of investigators in the Departments of Medicine and Pediatrics, as well as clinical investigators based at the Tufts Human Nutrition Research Center for the Study of Aging. The needs of the investigators who form the users group are primarily for repetitive analyses of amino acids. 13C-leucine is used to study protein metabolism under the conditions of hypocaloric dietary therapy, exercise, and Crohn's disease. 6,6,d2-glucose is used to study the interrelationships of glucose and protein under hypocaloric dietary connections, glucose metabolism during a euglycemic clamp, and glucose recycling in normal and diabetic humans. A novel proposal utilizes d2-folate to examine folate turnover in aging humans. Incorporation of d3- leucine into apolipoproteins is used as a tracer and to assess apolipoprotien turnover. Although several of the major users have established collaborations with GC-MS Centers elsewhere in the Boston area, several developments already limit the availability and utilization of these instruments. Heavy competition with other investigators using stable isotope technology already exists: long delays in sample analysis are common. These hamper the analysis of the pilot studies necessary to the design and conduct of more intrusive investigations. Second, the delay of results of earlier studies mean that additional cannot be initiated. Both of these factors limit the expansion of research projects already receiving PHS support. Finally, because these instruments are not committed to the support of Tufts investigators, analysis of our specimens is accorded a low priority, and makes our future of these methods tenuous. Acquisition of a GC-MS at our institution would relieve the analytic pressure we now face, and assure the completion of projects already underway. Furthermore, this instrument would improve our potential for related research in the future, and expose new clinical investigators to stable isotope technology.